THE AMERICAN BOTANIST 



159 



plants, and the cohesion of sap is still greater, often amounting 

 to a pressure of 200 atmospheres. In the stems of plants, then, 

 the water and sap are in practically solid columns extending 

 from the leaves down tO' the roots. When, therefore, water is 

 abstracted from the cells of the leaves by evaporation or other 

 processes of the plant, the pull exerted is transmitted down- 

 ward to the roots and more water is taken in. A book by Dr. 

 Dixon in which the subject is discussed at length with much 

 experimental proof has just appeared from the press of The 

 Macmillan Co. It is entitled "Transpiration and the Ascent of 

 Sap in Plants." It is undoubtedly one of the most important 

 contributions to physiological botany that has appeared for 

 some time and seems to have cleared up a problem which has 

 long perplexed plant students. The price of the book is $1.40 

 net. 



In ''Studies of Trees," J. J. Levison, who is Forester to 

 the Department of Parks, Brooklyn, N. Y., has given us still 

 another kind of tree book. Most of those with which we are 

 familiar aim solely at identification. The present book goes 

 farther and discusses the best trees for lawns, streets and wood- 

 lands and how to plant them, the important insect and fungus 

 pests with means for their eradication, pruning and tree repair, 

 forestry, and the uses of wood. The first half of the book is 

 taken up with a description of our common trees under such 

 heads as distinguishing characteristics, form, size, range, soil, 

 enemies, commercial value, common names, and comparison 

 with other trees. All the information given is useful, but the 

 lack of a key to the trees themselves must render this largely 

 a sealed book tO' the beginner, at least as far as identifying" the 

 trees is concerned. Those who know the trees will find much 

 in the book of interest. There are 150 illustrations of specimen 

 trees, examples of bark and wood and of the insect enemies 

 of the trees. The book is issued by John Wiley and Sons, New 

 York, and costs $1.00. 



